At the moment the umbilicus separates from the fetus during the birthing process, several physiologic functions formerly supported by the dam must become operational in the neonate to ensure survival of the calf. These functions include the ability to maintain adequate oxygen saturation of blood, to regulate acid-base balance, to engage endogenous metabolic pathways for energy production, and to preserve body temperature within critical limits. This article reviews cardiopulmonary function, acid-base balance, and energy metabolism in the fetus and neonate.